Liquid simulation on MacOS

[neilwth]

After pulling the latest src with this PR, the float32/64 issue resolved, but I still got the following issues with backend gs.metal:

[Genesis] [11:36:48] [WARNING] pbs sampler failed. Falling back to random sampler.

and

[Genesis] [11:36:58] [INFO] Compiling simulation kernels... RHI Error: cannot create compute pipeline state: Compiler encountered an internal error (code=3) RHI Error: cannot create compute pipeline state: Compiler encountered an internal error (code=3) Assertion failed: (p != nullptr), function bind_pipeline, file metal_device.mm, line 382.

Still, the script works fine but slowly with cpu, and simulations without liquid are OK for both cpu and metal.